Protected transformer circuit for high-voltage tubes



Feb. 8, 1949. GATES 2,461,265

PROTECTED TRANSFORMER CIRCUIT FOR HIGH-VOLTAGE TUBES Filed Sept. 17,1945 E9 y- INVENTORI Herbe rt H. Ga 1:85

ATTORN Patented Feb. 8, 1949 UNITED STATES OFFICE PROTECTED TRANSFORMEB.CIRCUIT FQR 2 Claims. 1

The present invention relates to a protected transformer circuitdesigned particularly for use in connection with the operation at highvoltages of luminous discharge tubes, such as those employed in neonsigns, or for cold cathode lighting, or for other similar applications.

In the operation of such luminous discharge tubes, a high potential isrequired, which may range between 4000 and 15,000 volts, and such tubesare usually energized from transformers,

the primary windings of which are connected to ordinary commerciallighting circuits at 110 or 220 volts. With a tube so energized, it isobvious that should the tube break, or should the secondary circuit bebroken, the open circuit secondary voltage will rise far above itsrating, and the transformer will constitute a menace to life, as Well asa fire hazard. Such a condition cannot be corrected by the use of anordinary fusible cut-out in the primary circuit of the transformer, r

for should the secondary of the transformer be open circuited, thecurrent in the primary winding would be at its minimum value.

According to the present invention, there is provided an improvedprotected circuit for high voltage tube transformers, whereinprcvisicnis made for the automatic interruption cf the primary circuitof the transformer should the tube break or should the secondary circuitbe broken or faulted, with a resulting falling of! pi the currenttraversing the primary winding. Furthermore, the circuit is so arrangedthat the primary winding of the transiormer cannot be accidentallyenergized before the trouble i the secondary circuit has been clearedand the arrangement is sate to operate. The above and other advantageousfeatures of the invention will hereinafter more fully appear from theIollowins description considered in connection with accompanyingdrawings, in Which- Fig. 1 is a diagrammatic View Of a circuit em.-bodying the present invention in non-operating condition.

Fig. 2 illustrates the circuit of .Fig. 1 in condition for operating aluminous discharge tube.

Fig. 3 illustrates the functioning of the circuit to de-energize theprimary winding upon the occurrence of an abnormal conditioninthesecondary circuit.

Figs. 4, 5 and 6 are fragmentary viewsillnstrating the operation of aspecial switch for controlling the primary circuit.

.Fig. 7 is a front view of the switch ,of Rig. .4.

Re rin to the ing he circu t .of the invention is shown in connectionwith a luminous discharge tube T, which may be of any desired type suchas is customarily employed in connection with advertising signs, or coldcathode righting. The electrodes of the tube T are connectedacross theterminals of the secondary winding S of a transformer, the primarywinding of which is indicated at P. The transformer is so designed as toprovide a voltage across its secondary S, sufficiently high to start andoperate the tube T.'

One terminal of the primary winding P is connected to one of a pair ofalternating current supply mains i energized from a commercial source,as indicated, while the other terminal of winding P is connected inseries with the winding 2 of a protective relay device 3. The relay 3further comprises a pivoted contact 4 movable with the relay armature,and one terminal of the winding 2 is connected to the contact 4. Thefree end of the contact 4 is spaced from a stationary contact 5 when therelay winding 2 is in a deenergized condition, as shown in Fig. 1. Therelay Contact 5 is adapted to be connected to the other supply rnain byclosure of a knife switch 6,

= which is shown open in Fig. 1.

in order to provide for initial pulling in of the relay 3 icllcwingclosure of the knife'fswitch' 6, a push button switch 7 is provided, thenormally open contacts 8 of which are connected in shunt around theknife switch 6 and the relay contacts 4 and 5. Therefore, a momentaryclosure ofthe push button switch I, after closure ofthe knife switch 6,as indicated in dotted lines in Fig. 2, will cause sufficient current totraverse the relay winding 2 to pull in the armature and engage themovable contact 4 with the stationary contact 5.

Engagement of the relay contacts 4 and 5 as the armature pulls upestablishes a holding circuit ier the relay, even though the push buttonswitch released and returned to the full line re men of F s- ,2- h refth P imary i idin g P of the transformer is energized and the resultinghigh voltage of the secondary 8 starts the tube T and mainta n i s i l mnat on. G nally speaking. the starti g of the t be T i 50 Quick th t themomentar closure of the push b tt n c n a t e u fi eni to st t the 9? ad ca se the relay winding 2 to .draw sufic ent cur-r n to ho the ,on.acts .4 a d .5 closed. and th act that these nta ts closed is indicatedby the illumination .of a suitable pilot light 9 ridged .across theterminals of the prima y wind n P As dong ,as the discharge ,tube Tremains in operative condition, with the circuit of the secs and inengagement.

However; should the tube T break, or should the circuit of the secondarywinding s be broken,

as indicated in Fig. 3, the current in the primary winding P will dropsharply, although the open 4 angularly spaced bridging members 13 and I4of conducting material that are adapted to cooperate with pairs ofspaced stationary contacts it, respectively. The contacts I? are adaptedto be connected in the circuit of Fig. i in the same manner as are thepush button contacts 8, while the contacts 1% are connected between therelay contact 5 and one supply main I. Therefore, engagement of thecontacts by the bridging member is will be equivalent to closing thepush button switch, while engagement of contacts it by bridging member Ii will be the equivalent of closing the knife switch 6.

secondary voltage will rise to its rated value.

When this occurs, the winding 2 willno longer hold up the relayarmature, and the movable contact 5 will separate from the stationarycontact 5, as shown in Fig. 3. The resulting opening of the primarycircuit of the transformer will deenergize the secondary circuit so thatdangerous high voltage conditions no longer exist. The opening of theprimary circuit of the transformer will be indicated by extinguishmentof the pilot light 9, so as to call attention to the fact that thecircuit is no longer operative. I As previously pointed out, the relayit is so designed that normal operating current traversing the winding 2when the tube is running is sufficient to hold up the relay armature tomaintain the relay contacts 4 and 5 in engagement, whereas the greatlyreduced current through the primary circuit, in the event of trouble,will not be suflicient to hold the relay closed. Obviously, the design.of any particular winding 2 for the relay 3 will depend upon. the ratingof the transformer and the size of the tube T. As one illustrativeembodiment of the invention, the relay winding 2 may be designed to holdthe relay contacts closed, with a current range of between 1.5 to 2.5amperes, with the relay dropping out to open the contacts 4 and 5whenever the current falls appreciably below 1 ampere.

Assuming that the relay 3 has dropped out as a result of a fault in thetube circuit, as indicated in Fig. 3,the secondary circuit ofthetransformerwillremain dead, while the relay 3 remains open, and thereis no possibility of any one being injured by the high'voltage of thesecondary circuit, even though the knife switch 6 may be left closed,through inadvertence. Whenthe extinguishment of the pilot light t callsattention to the fact thatprimary circuit has been opened, the normalprocedure would be to open the knife switch until the tube has beenreplaced, or necessary repairs made to the secondary circuit; However,when once the relay has dropped out due to trouble in the secondarycircuit, accidental closure of the knife switch 6 can do no harm, sincethe circuit of the relay winding 2 can be ire-established only throughoperation of the push button I which is mounted apart from the knifeswitch 6.

Referring now to Figs. 4, 5 and 6, there is shown a modification of thecircuit, wherein the functions of knife switch 6 and the push button ;'lare incorporated in the movable element of a single switch of the snapaction type, usually employed for wall switches. In Fig. 4, the movableelement of such a switch is shown in the form of a rotatable disk I 8 ofinsulating material turnable about a pivot H, with the diskbeing'maintained in the off position through the pull of a spring I 2below the pivot I l. The disk carries With the disk it of the snapswitch in the off position of Fig. 4, the circuit is in the nonpcratingcondition of Fig. 1. When it is desired 0 energize the tube T, theswitch is moved to he on position of Fig. 6, which movement occurs witha snap action, due to the pull of the spring above the pivot ll. Whenthe snap switch is so moved from the oif to the on position, it passesthrough the intermediate position of Fig. 5,'so that the contacts !-5are bridged by the mber is to energize the relay winding 2, mo- Itarily, before the contacts 56 are bridged by the member it. Therefore,moving the switch to the on position has the effect of momentarilyestablishing the circuit of the relay winding 2, so that bridging of thecontacts It immediately thereafter holds up the relay. However, movementof the disk H] from the position of Fig. 5 to the position of Fig. 6 hasthe effect of unbridging the contacts l 5 as the member is moves pastthese contacts into the position of Fig. 6, where only the contacts arebridged by member M.

As previously pointed out, when opening of the relay 3 breaks theprimary circuit and extinguishes the pilot light 9, the normal procedureis to open the knife switch 6 before working on the secondary circuit.The same applies to the snap switch shown in Fig. 4, which is operatedto the off position upon the occurrence of conditions causing the relay3 to open.

In order to prevent premature operation of the switch to the closedcondition of Fig. 6, before the secondary circuit has been cleared oftrouble, a latch I1 is associated with the operating portion [9a of themovable disk II which serves to hold the switch in off position. Asshown in Fig. 7, this latch I! must be pulled out by hand before theportion HM can be moved upwardly from the off position, therebypreventing closure of the primary circuit by accidental operation of thesnap switch. 1 I claim:

1. In a circuit for high voltage illumination having, a transformerincluding a primary and a secondary winding, an illuminating deviceconnected across said secondary winding, an alternating current sourceof electrical energy, one side of said primary winding being connectedto one side of said energy source, and a normally open underload relayhaving its winding and one contact connected in series with the otherside of said primary winding and having a second contact adapted to beconnected with the second side of said energy source; the improvementwhich consists in the provision of a rnanually operable unitary switchmovable from an open to a closed position with a snap action, saidswitch having contacts in circuit with said relay winding andthe secondside of said energy source seas to establish momentarily, upon aninitial vement of said switch to an intermediate position between openand closed, a circuit around the open contacts of said relay and betweensaid relay winding and the second side of said energy source to causesaid relay to pull in and close its normally open contacts, and contactsin circuit with the second contact of said relay and said second side ofsaid energy source so as to maintain, upon a final movement of saidswitch to a second position, said relay contacts closed as long as acurrent of predetermined value traverses the primary circuit.

2. In a circuit for high voltage illumination having, a transformerincluding a primary and a secondary winding, an illuminating deviceconnected across said secondary winding, an alternating current sourceof electrical energy, one side of said primary winding being connectedto one side of said energy source, and a normally open underload relayhaving its winding and one contact connected in series With the otherside of said primary winding and having a second contact adapted to .beconnected with the second side of said energy source; the improvementwhich consists in the provision of a manually operable and spring-biasedsingle-throw switch having contacts in circuit with said relay windingand the second side of said energy source so as to establishmomentarily, upon an initial movement of said switch to an intermediateposition between open and closed, a circuit around the open contacts ofsaid relay and between said relay winding and the second side of saidenergy source to cause said relay to pull in and close its normally opencontacts, contacts in circuit with the second contact of said relay andsaid second side of said energy source so as to maintain, upon a finalmovement of said switch to a second position, said relay contacts closedas long as a current of predetermined value traverses the primarycircuit, and manually operable means for locking said switch in itsinitial or open position thereby to prevent inadvertent use of saidswitch.

HERBERT H. GATES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 472,084 'I'hum Apr. 5, 18922,249,457 Catlett July 15, 1941 2,305,096 McDermott Dec. 15, 19422,308,987 Lotto Jan. 19, 1943 2,309,711 Pearson Feb. 2, 1943 2,310,149McDermott Feb. 2, 1943

